The co-occurrence of medullary thyroid carcinoma (MTC) and papillary thyroid carcinoma (PTC) is thought to be a rare phenomenon. Here, we present a patient undergoing surgery due to a suspected MTC. Histopathological workup confirmed the suspected diagnosis but also described an incidental PTC in the contralateral lobe with lymph node metastasis in the central cervical compartment. A 58-year-old female presented with thyroid nodules and significantly elevated levels of calcitonin and carcinoembryonic antigen (CEA). She underwent total thyroidectomy along with central and bilateral lymph node dissection. Histology revealed a MTC of 20 mm and a BRAF V600E-positive PTC of 11 mm with central cervical lymph node metastasis. Postoperatively, ablative radioiodine therapy was performed. Two months later, both calcitonin and CEA were normalized. Simultaneous occurrence of MTC and PTC seems to be rare, but recent literature suggests that simultaneous occurrence is probably more frequent than initially thought. Preoperative calcitonin can be helpful in the diagnostic workup of thyroid nodules. Due to different treatment strategies, precise histological differentiation of potential lymph node metastasis is essential.